One Nation’s Pauline Hanson hands out how-to-vote cards outside a polling booth in Brisbane. Hanson has said One Nation will not give Labor preferences until it puts Greens last on how-to-vote cards.
Photograph: Dan Peled/EPA

Pauline Hanson has told the Labor leader, Bill Shorten, she will not “flow preferences” to Labor in the looming Longman byelection, or federally, unless the ALP puts the Greens last on how-to-vote tickets.

In response Shorten has accused the One Nation leader of “attempting to direct the preferences of Longman voters to the LNP” and criticised her for turning her back on the battlers by signing on to the Turnbull government’s ambition to cut taxes for Australia’s biggest corporations.

The spat between the leaders has played out in an exchange of letters, seen by Guardian Australia, following the high court’s decision last week in the Katy Gallagher case – a decision that has triggered a super Saturday of byelection contests including in the Queensland seat Labor holds by 1,390 votes.

The mini-election season looms as a significant test for both Malcolm Turnbull and Bill Shorten, with the major parties set to campaign on rival tax plans outlined during budget week.

A ReachTel poll published on Saturday suggests Labor will struggle to hold the Queensland seat of Longman, and One Nation is likely to be a significant factor in the result. If the survey is correct, Hanson’s party is currently polling 15% in the electorate.

Labor snatched the seat at the last election in part because of a favourable preference flow from One Nation, but the party’s candidate for the byelection, Matthew Stephen, has already made it clear publicly he wants to preference Labor last in the contest. On current indications that would help deliver the seat back to the LNP.

Quick guide

Australia's dual citizenship crisis

The constitution

Section 44 (i) of Australia's constitution bars "citizens of a foreign power" from serving in parliament, including dual citizens, or those entitled to dual citizenship. But the provision was very rarely raised until July 2017, when the Greens senator Scott Ludlam suddenly announced he was quitting parliament after discovering he had New Zealand citizenship.

That sparked a succession of cases, beginning with Ludlam’s colleague Larissa Waters, as MPs and senators realised their birthplace or the sometimes obscure implications of their parents’ citizenship could put them in breach.

An incumbent federal government has not won a seat back from an opposition at a byelection for a century, but the share of the major party vote has been falling, and the strength of insurgent parties, like One Nation, will influence results in different parts of the country.

Hanson wrote to Shorten on Thursday “seeking an assurance from you as leader of the Australian Labor party that you will guarantee placing the Greens at the bottom of all Labor how-to-vote cards”.

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The One Nation leader says she cannot “in good conscience flow One Nation preferences to Labor if their preference relationship continues with the Greens”.

Shorten replied on Sunday saying: “I know you are under a lot of pressure following your decision to support the prime minister’s $80bn tax handout to multinationals and the big banks.

“That’s the only explanation I can think of for your letter to me, in which you appear to be attempting to direct the preferences of Longman voters to the LNP.

“When Queenslanders voted for you at the last election, you should have been honest with them about your true intentions. You should have told them you would vote with Turnbull 90% of the time.”

He says Labor will not do a deal with One Nation either in Longman or in the federal election. “Sadly, you’ve put the top end of town first and Aussie battlers last – so that’s where Australian Labor will put One Nation in our preferences at the next election.”

“Your voting record in Canberra has left us with no choice but to put you at the back of the queue – because we’ll always put working Australians and their families first.”

The ReachTel survey of 1,277 residents across the federal electorate of Longman taken on Thursday night has the LNP polling ahead of Labor on two-party-preferred terms 53% to 47%.

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But the research, funded by the Australia Institute, also suggests Labor has issues on which it can campaign.

The Turnbull government’s proposal to cut tax for Australia’s biggest businesses is unpopular in the seat, with only 17% endorsement. A majority of respondents (53.7%) also thought the third phase of the income tax cuts proposed by the Turnbull government in last week’s budget, to flatten the tax rate on incomes between $41,000 and $200,000, was unfair.

Voters were asked whether they supported or opposed tax cuts delivering an average of $530 a year extra for low and middle income earners in the first four years, and tax cuts for high income earners in seven years time.

More Longman voters opposed the measure (47.3%) than supported it (38.3%).